Air conditioning systems, such as roof top units that cool the air inside a building, rely on the efficient transfer of heat from a refrigeration fluid to the air through heat exchangers. Heat exchangers generally comprise a “heat exchanging coil” comprising one or more tubes interconnected by a plurality of thin metal fins that serve to increase the surface area of the tubes that is exposed to the air. As compressed refrigeration fluid passes through the tubes, a fan draws unfiltered air through the fins and around the tubes to facilitate cooling of the refrigeration fluid inside the tubes. The unfiltered air tends to carry dirt and debris from the surrounding environment, some of which becomes trapped in the spaces between the tubes and the fins. The efficiency of a heat exchanging coil in transferring heat from a refrigeration fluid to the air depends on how freely the air moves through the spaces between the tubes and the fins. If the spaces between the tubes and the fins are clogged by dirt and debris, the efficiency of a heat exchanging coil drops significantly.
Regular maintenance of the heat exchanging coil is important to maintain efficient heat transfer. Traditionally, heat exchanging coils are cleaned in a variety of ways, including, but not limited to, the use of high pressure “pressure washers.” Pressure washers force high-pressure (1000 pounds per square inch (“psi”) or higher) air or water through a small, usually hand-held nozzle that directs high-pressure air or water toward the heat exchanging coil to blow dirt and debris from the spaces between the tubes and the fins. The effective cleaning area of the air or water stream is approximately the size of the small nozzle orifice, which may be one-eighth inch to three-eighths of an inch (⅛–⅜″) in diameter in some cases. Significant labor costs are incurred when using small orifice, high-pressure nozzles because of the number of passes that must be made by the operator to clean a desired region of the heat exchanging coil.
The use of water-based pressure washers has several disadvantages. Water-based pressure cleaners typically require even higher pressures than do air-based pressure cleaners, because water has a much higher drag coefficient than air and is more difficult to “push” through a typical heat exchanging coil. Moreover, the large volume of water gallons per minute typically needed to clean a heat exchanging coil can cause damage to other components of an air conditioning system, which could lead to an electrical short in the circuitry of the air conditioning system. Further, the use of a large volume of water can cause damage to an adjacent building or other surrounding materials near the air conditioning system that is being cleaned. In order to prevent this damage, significant labor time is required to mask-off air conditioner components and the surrounding building to prevent or limit water damage during water-based cleaning of a heat exchanging coil.
Any type of high-pressure cleaning method can cause damage to a heat exchanging coil because the high pressure tends to bend the fins and/or fold the fins over, which closes the space between the tubes and the fins and leads to a loss of heat exchanger efficiency. In addition, high pressure water cleaning methods always impose extreme force on the coil bundle which can loosen the tight fit between the fin and tube causing reduced efficiency and mechanical damage. Thus, there is a need for an improved system for cleaning heat exchanging coils that reduces the labor time required to clean a coil, reduces the risk of damage to the coil fins, reduces the labor time needed to mask and clean a coil, and reduces the possibility of damage to the building on which the heat exchanging coil is installed.